A predictive model for reproductive performance following abortion in Thoroughbred mares

Area of Science:

• Veterinary Medicine
• Reproductive Biology
• Equine Science

Background:

• Pregnancy losses in mares, including early embryonic death (EED) and abortion, cause significant economic and production losses, particularly Equid herpesvirus (EHV-1) abortion epizootics.
• The long-term impact of EHV-1 and other abortions on the subsequent reproductive performance of broodmare populations remains largely undefined.

Purpose of the Study:

• To investigate the relationships between EED and abortion and subsequent reproductive outcomes in Thoroughbred mares.
• To develop predictive models for the influence of reproductive variables on performance following EHV-1 and other abortion causes.

Main Methods:

• A prospective cohort study was conducted on two South African farms following EHV-1 epizootics.
• Reproductive outcomes analyzed included breeding efficiency, month of last breeding, subsequent pregnancy rates, and live foal rates.

Main Results:

• Early embryonic death (EED) was a significant predictor of all reproductive outcomes studied.
• Abortion was associated with increased breeding effort and a later breeding month to achieve pregnancy, but did not affect pregnancy or foaling success.
• Increasing age negatively impacted reproductive efficiency, pregnancy, and foaling probabilities. Mare reproductive status and the last month of breeding were also significant predictors.
• Breeding in the first month of the season improved pregnancy probability in barren mares.

Conclusions:

• EED is a critical factor influencing overall reproductive performance in Thoroughbred mares.
• While abortions necessitate greater breeding effort, EED has a more pervasive effect on subsequent reproductive success.
• Management strategies should consider EED and breeding timing to optimize mare reproductive efficiency.